Revision of the taxonomic status of the species Rhizobium leguminosarum (Frank 1879) Frank 1889AL, Rhizobium phaseoli Dangeard 1926AL and Rhizobium trifolii Dangeard 1926AL. R. trifolii is a later synonym of R. leguminosarum. Reclassification of the strain R. leguminosarum DSM 30132 (=NCIMB 11478) as Rhizobium pisi sp. nov.

The taxonomic status of the species Rhizobium leguminosarum, Rhizobium trifolii and Rhizobium phaseoli was analysed in this study on the basis of their molecular and phenotypic characteristics. According to the results, the type strain R. phaseoli ATCC 14482(T) does not belong to any of the already described species of the genus Rhizobium and it should therefore be considered as a different species. In contrast, the strains of R. trifolii examined belonged to R. leguminosarum and thus R. trifolii is a later synonym of R. leguminosarum. The results of the analysis of 16S-23S intergenic spacer region and rrs, recA and atpD gene sequences as well as those of DNA-DNA hybridization experiments and phenotypic characterizations showed that the type strains R. leguminosarum USDA 2370(T) and R. leguminosarum DSM 30132 do not belong to the same species. Taking into account that strain USDA 2370(T) corresponds to the original strain of this species, 3Hoq18(T), this strain should be considered as the true type strain of R. leguminosarum whereas strain DSM 30132 should be reclassified as a different species, for which the name Rhizobium pisi sp. nov. is proposed (type strain, DSM 30132(T)=NCIMB 11478(T)).